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THE  INFLUENCE  OF  PASTEUR 
ON  MEDICAL  SCIENCE 


THE  INFLUENCE 
OF  PASTEUR  ON 
MEDICAL  SCIENCE 

fore  t\)t  ^peuical  ^t\)oo\  of 
3|ot)ns  J^opbins?  mnitjer^it^ 

BY 

CHRISTIAN  ARCHIBALD  HERTER,  M.  D. 


NEW  YORK 

DODD,  MEAD  &  COMPANY 

M  C  M  I  V 


Copyright,  1904, 
By  Christian  Archibald  Herter 


en 


on 


THE  INFLUENCE  OF  PASTEUR 
ON  MEDICAL  SCIENCE 


'*«»*^ 

i^ 


THE  INFLUENCE  OF 
PASTEUR  ON  MEDICAL 
SCIENCE 


TO  one  who  treasures  mem- 
ories of  student  days 
spent  in  your  patholog- 
ical laboratory,  when 
each  member  of  a  small  and  fa- 
vored group  worked  under  the 
personal  guidance  of  the  great 
teacher  whose  unselfish  labors 
have  done  so  much  for  science  in 
this  country,  it  is  indeed  an  ex- 
ceptional privilege  to  address 
those  who  represent  the  School 
of  Medicine  that  has  grown  since 
then  to  be  the  model  for  many  an 
older  institution.  Yet  I  am  con- 
scious that  this  very  privilege  en- 
tails a  risk, — proportioned  to  the 


THE   INFLUENCE   OF  PASTEUR 

largeness  of  the  opportunity, — of 
using  unworthily  the  precious 
moments  which  fortune  has  be- 
stowed on  me.  My  choice  of 
subject  has  not,  I  fear,  lessened 
this  hazard,  for  I  have  chosen  to 
speak  to  you  of  one  of  the  most 
significant  men  of  the  past  cen- 
tury, whether  we  consider  him 
as  a  person,  as  an  investigator  or 
as  a  public  benefactor.  I  pray 
you,  therefore,  deal  gently  with 
the  shortcomings  of  an  undertak- 
ing so  difficult  and  ambitious  as 
that  of  estimating  the  influence 
of  a  great  career  on  the  advance 
of  medical  science. 

Louis  Pasteur  first  saw  the  light 
of  day  on  December  27th,  1822, 
in  an  humble  dwelling  in  the  little 
town  of  Dole  in  the  Franche 
Comte.  His  parents  had  small 
means  and  limited  social  oppor- 
tunities, but  through  the  exercise 


ON   MEDICAL   SCIENCE 

of  forceful  character  and  unusual 
fidelity  to  elevated  ideals  of  life 
managed  to  give  him  a  fair  ele- 
mentary education.  The  father, 
earnest,  industrious  and  intellec- 
tually ambitious,  instilled  into  his 
son  the  desire  to  become  a  useful 
and  respected  member  of  society, 
shielded  him  by  constant  com- 
panionship from  the  vulgar  temp- 
tations of  youth,  and  fired  him 
with  a  love  of  country  which  a 
long  and  honorable  career  as  a 
soldier  of  Napoleon  had  strongly 
fortified.  The  mother  of  young 
Pasteur  was  prevented  by  house- 
hold cares  from  sharing  closely 
the  intellectual  interests  of  her 
only  son,  but  showed  the  depth 
of  her  affection  by  making  many 
a  little  sacrifice  to  further  his  edu- 
cation. She  was  a  spirited  wo- 
man, possessed  of  lively  imagina- 
tion and  quick  intelligence,  and 


THE   INFLUENCE   OF   PASTEUR 

it  is  reasonably  clear  that  the  un- 
usual artistic  perceptions  of  Pas- 
teur mark  the  perpetuation  of 
these  maternal  gifts.  Although 
the  school  days  of  Pasteur  appear 
to  have  given  little  indication  of 
an  exceptional  future,  the  lad 
showed  some  qualities  which  dis- 
tinguished his  work  in  later  life. 
In  his  daily  tasks,  at  which  he 
workedfaithfully  and  deliberately, 
he  showed  the  most  scrupulous 
accuracy  and  truthfulness,  attri- 
butes which  are  the  more  note- 
worthy for  the  reason  that  they 
belonged  to  a  temperament  en- 
riched with  a  strong  vein  of  ro- 
manticism ,  which  for  a  time  found 
expression  in  a  fervid  devotion  to 
poetic  literature.  Moreover,  Pas- 
teur showed  while  still  in  his  teens 
a  pronounced  capacity  for  por- 
traiture. During  his  three  years 
of  instruction  at  the  College  Royal 


ON   MEDICAL   SCIENCE 

of  Besanf  on,  which  he  entered  at 
eighteen  years  of  age,  the  young 
student  was  more  absorbed  in 
literature  and  art  than  in  science, 
and  impressed  his  colleagues  as 
being  surely  destined  for  an  artis- 
tic career.  The  courtesy  of  Mr. 
Philip  B.  Marcou  of  Cambridge 
has  made  it  possible  for  me  to 
examine  closely  two  fine  exam- 
ples of  Pasteur's  work  at  the  end 
of  this  Besanf  on  period.  Although 
these  portraits  disclose  the  man- 
ual hesitancy  of  the  imperfectly 
trained  craftsman,  they  bear  an 
unmistakable  air  of  distinction 
and  are  executed  with  a  respect 
for  detail  which  is  highly  remark- 
able. Anyone  who  sees  these 
youthful  works  is  likely  to  feel 
that  eyes  so  sensitive  to  these 
minutest  particularsof  form  would 
be  apt  to  see  many  things  which 
others  had  failed  to  notice;  and  it 


THE   INFLUENCE   OF   PASTEUR 

is  noteworthy  that  Emil  Fischer, 
whose  calm  judgment  is  well 
known,  has  expressed  his  belief 
that  Pasteur's  crystallographic 
discoveries  were  facilitated  by  his 
artistic  perceptions. 

The  years  at  Besan^on  were 
followed  by  a  highly  important 
course  of  study  at  the  Ecole  Nor- 
male  of  Paris,  during  which  Pasteur 
formed  the  determination  to  de- 
vote himself  to  science.  For  the 
first  time  in  his  life  the  gifted,  im- 
pressionable young  man  found 
himself  under  the  influence  of  a 
creative  scientific  mind  of  the 
highest  order — a  mind  which  has 
left  a  large  and  permanent  mark 
upon  the  history  of  chemistry, 
and  which  could  not  fail  power- 
fully to  mould  the  plastic  intelli- 
gence of  Louis  Pasteur.  Jean 
Baptiste  Dumas,  who  had  already 
discovered  the  great  principle  of 


ON    MEDICAL   SCIENCE 

substitution,  united  to  his  genius 
as  an  investigator  the  charm  of  a 
finished  and  spirited  delivery. 
His  Sorbonne  lectures  fairly  cap- 
tivated the  young  student  and 
gave  definite  and  lasting  direction 
to  his  study  and  fancy,  and,  later, 
to  his  researches.  Other  teachers 
of  a  superior  order  contributed  to 
lead  Pasteur  into  the  promising 
and  fascinating  paths  of  physics 
and  chemistry.  The  attractive 
Balard,  to  whom  bromine  had  first 
surrendered  the  secret  of  its  ex- 
istence, reinforced  the  chemical 
teachings  of  Dumas,  and  the  ad- 
mirable lectures  of  Delafosse 
aroused  an  enduring  interest  in 
the  subtle  beauty  of  crystalline 
forms.  But  it  is  to  the  strong 
intellect  of  Dumas  that  Pasteur 
owed  his  first  grasp  of  the  great 
principles  of  science  and  that  en- 
thusiasm for  work  which  made  it 


THE   INFLUENCE  OF  PASTEUR 

possible  to  ignore  the  harsh  and 
depressing  material  conditions 
that  prevailed  at  the  Ecole  Nor- 
male.  The  recognition  by  young 
Pasteur  of  the  importance  of  cor- 
relation in  the  physical  sciences 
is  an  impressive  feature  of  his 
mind  at  this  period  of  close  asso- 
ciation with  great  chemical  inves- 
tigators. Evidences  of  this  recog- 
nition exist  in  a  singularly  fine 
letter,  full  of  enthusiasm  for  sci- 
ence, which  he  wrote  to  his  col- 
league, Jules  Marcou,  then  enter- 
ing on  his  distinguished  career  as 
a  geologist.*  ''Before  finishing 
your  letter,"  says  young  Pasteur, 
*'  I  had  already  regretted  that  your 
studies  in  chemistry  were  incap- 
able of  responding  to  what  geol- 

*  Mr.  Philip  B.  Marcou  has  permitted  me  to  read  a 
large  number  of  unpublished  letters  written  by  Pas- 
teur to  his  father.  The  letter  above  quoted  is  dated 
June  ID,  1845,  and  is  one  of  a  very  small  number  be- 
longing to  this  period. 

10 


ON    MEDICAL   SCIENCE 

ogy  will  often  ask  of  them."  .  .  . 
'M  know  very  well  that  many 
distinguished  geologists  have  no 
broad  conception  of  chemistry, 
but  I  believe  this  to  be  a  great 
pity,  and  I  think  that  geology  has 
not  often  enough  turned  to  chem- 
istry." The  chemist  of  twenty- 
three  summers  held  a  point  of 
view  which  was  destined  very 
soon  to  aid  him  in  a  memorable 
research. 

It  was  in  the  field  of  crystal- 
lography that  Pasteur,  led  by  an 
interest  in  the  ingenious  and  deli- 
cate methods  of  the  science,  first 
showed  his  exceptional  capacity 
to  observe  minutely  things  and 
processes,  and  to  correlate  and 
interpret  his  observations.  He 
began  by  carefully  repeating  a 
series  of  crystal  measurements  on 
tartaric  acid,  racemic  acid  and 
their  salts,  shortly  before  pub- 
II 


THE   INFLUENCE   OF   PASTEUR 

lished  by  Provostaye.  During  the 
study  of  the  recrystallized  salts  of 
tartaric  acid  he  observed  one  very 
important  but  unobtrusive  thing 
which  the  distinguished  physicist 
had  overlooked  —  regular  evi- 
dences of  hemihedral  facets.  All 
the  tartrates  showed  a  weak  kind 
of  isomorphism,  which  is  appar- 
ently forced  on  them  by  the  tar- 
taric acid  group,  whatever  other 
element  may  exist  in  the  com- 
pound. Guided,  as  he  tells  us, 
first,  by  the  observation  of  Biot 
that  tartaric  acid  and  its  compound 
rotate  the  plane  of  polarization; 
secondly,  by  a  relationship  be- 
tween the  crystalline  form  of 
quartz  and  the  direction  of  rota- 
tion ;  and,  finally,  by  Delafosse's 
conception  that  hemihedrism  de- 
pends on  definite  crystallographic 
laws,  Pasteur  concluded  that  there 
is  a  relation  between  the  hemi- 

12 


ON   MEDICAL  SCIENCE 

hedrism  of  the  tartrates  and  their 
optical  activity.    An  unexpected 
discovery  soon  proved  this  to  be 
true  in  a  conclusive  and  beautiful 
manner.    One  day,  in  the  dark 
library  of  the  Ecole  Normale,  Pas- 
teur's eyes  lighted  on  a  remarka- 
ble paragraph  from  the  writings 
of  the  Berlin  chemist  and  crystal- 
lographer,   Mitscherlich,   relative 
to  two  different  saline  combina- 
tions of  tartaric  acid,  the  tartrate 
and  the  paratartrate  (or  racemate) 
of  sodium  and  ammonium.  This 
note  stated  that  these  two  types 
of  double  salts  have  the  same 
chemical  composition,  the  same 
crystal  form  with  equal  angles, 
the  same  specific  gravity,    the 
same  double  refraction,  and  that 
in  consequence  of  this  their  opti- 
cal axes  form  the  same  angles. 
Their  water  solutions  have  the 
same  refraction.    The  dissolved 
13 


THE   INFLUENCE  OF   PASTEUR 

tartaric  acid  salt  rotates  the  plane 
of  polarization  and  the  racemic 
salt  is  indifferent,  as  had  been 
found  by  Biot  for  the  whole  series 
of  salts.  ''  But,"  continues  Mit- 
scherlich^  *'the  nature  and  the 
number  of  atoms,  their  arrange- 
ment and  their  distance  from  one 
another  are  the  same  in  both  bod- 
ies." The  contradiction  expressed 
here  upset  all  Pasteur's  physico- 
chemical  ideas  and  persisted  for 
months  in  his  mind  like  an  inter- 
rogation point.  But  the  day  came 
when  experience  cleared  up  the 
mystery  by  demonstrating  that 
there  is  really  a  difference  between 
the  tartrates  and  the  racemates 
which  Mitscherlich  had  not  no- 
ticed. The  former  bore  hemi- 
hedral  facets  on  the  right  side  and 
always  rotated  the  plane  of  polar- 
ization to  the  right;  the  latter  bore 
facets  both  on  the  right  and  on 

«4 


ON   MEDICAL   SCIENCE 

the  left  sides  and  did  not  rotate 
polarized  light  at  all.  Moreover, 
it  later  appeared  that  this  inactive 
racemic  acid  may  be  caused  to 
crystallize  in  such  a  way  that  the 
crystal  mass  consists  of  equally 
numerous  dextro-rotary  and  levo- 
rotary  crystals,  the  former  pos- 
sessing hemihedral  facets  on  the 
right  side,  the  latter  hemihedral 
facets  on  the  left  side.  Both  kinds 
of  crystals  were  isomorphous,  but 
the  isomorphism  was  that  of  two 
asymmetric  crystals,  of  an  object 
to  its  reflected  image.  The  weighty 
and  surprising  discovery  had  been 
made  that  indifferent  racemic  acid 
crystallizes  into  equal  quantities 
of  ordinary  dextro-rotary  tartaric 
acid  and  the  newly  observed 
levo-rotary  tartaric  acid. 

This  research  on  the  tartrates, 
culminating  in  1848  with  the  dis- 
covery of  the  nature  of  paratar- 

»5 


THE   INFLUENCE   OF  PASTEUR 

taric  or  racemic  acid,  proved  that 
Pasteur  had  already  made  him- 
self master  of  the  experimental 
method. 

Three  distinct  practical  results 
followed  in  the  train  of  this  re- 
search as  a  consequence  of  con- 
tinued studies  of  crystallographic 
problems.  In  the  first  place  there 
came  to  light  numerous  fresh  ev- 
idences of  a  relation  between  mo- 
lecular constitution,  crystalline 
form  and  the  property  of  rotat- 
ing the  plane  of  polarization.  It  is 
true  that  Pasteur  seriously  enter- 
tained some  ideas  of  a  highly  spec- 
ulative nature  regarding  the  ope- 
ration of  dissymmetry  in  nature, 
ideas  which  involved  him  in  fruit- 
less experiments ;  but  on  the  other 
hand  the  tangible  and  positive  re- 
sults of  his  work  must  be  recog- 
nized as  forming  the  basis  of  the 
modern    doctrine  of  the  asym- 

i6 


ON   MEDICAL   SCIENCE 

metrical  carbon  atom,  which  has 
so  illuminated  our  ideas  of  the 
spatial  arrangements  of  the  atoms 
within  the  molecules  of  organic 
substance  ;  Secondly,  the  research 
on  the  tartrates  led  Pasteur  to  the 
recognition  of  a  series  of  optically 
inactive  compounds,  including  in- 
active malic  acid  and  inactive  am- 
yl  alcohol.  Finally,  the  crystallo- 
graphicresearcheswere  the  bridge 
over  which  the  far-seeing  investi- 
gator passed  on  the  way  to  lay  the 
foundation  of  a  new  biological  sci- 
ence, a  science  which  has  effected 
a  veritable  revolution  in  our  con- 
ceptions of  medical  problems. 
Cagniard-Latour,  Schwann  and 
Katzing,  by  knowledge  gained  in 
theirexperiments  on  alcoholic  fer- 
mentation, held  one  pass  to  the 
great  secret,  but  saw  not  the  fields 
of  discovery  to  which  it  might 
have  led  them.  Pasteur  made  his 

'7 


THE   INFLUENCE   OF   PASTEUR 

way  thither  by  a  singularly  trust- 
worthy intuition.  Greatly  im- 
pressed with  the  circumstance 
that  optically  active  substances 
like  the  sugars,  the  tartrates,  the 
malates,  the  citrates,  the  gums 
and  the  proteids,  seemed  to  be 
confined  to  the  organic  world  and 
were  not  to  be  found  outside  the 
tissues  of  plants  and  animals,  Pas- 
teur made  a  simple  yet  decisive 
experiment.  To  some  pure  crys- 
tallized inactive  ammonium  para- 
tartrate  he  added  fermenting  albu- 
minous material.  After  a  time  the 
fluid  was  examined  with  the  po- 
lariscope.  It  rotated  strongly  to 
the  left.  This  levorotation  was 
obviously  due  to  the  fact  that  the 
dextrorotary  constituent  of  the 
paratartrate  had  been  decom- 
posed. An  optically  inactive  fluid 
had  been  converted  into  an  opti- 
cally active  fluid.    According  to 

i8 


ON   MEDICAL  SCIENCE 

Pasteur's  theoretical  views  this 
striking  change  indicated  the  me- 
diation of  living  matter.  The  ac- 
tivity of  unorganized  purely  chem- 
ical ferments  could  not,  in  his 
judgment,  explain  the  facts  ;  mi- 
cro-organic life  must  be  in  some 
way  concerned.  Fortunately  the 
rnind  in  which  this  conception  was 
born  was  also  capable  of  testing 
its  correctness  by  the  most  rigid 
methods  of  investigation.  Fortu- 
nately, too,  the  external  condi- 
tions favored  a  studious  excursion 
into  the  processes  of  fermentation , 
for  Pasteur  was  called  in  1854  to  a 
Professorship  at  Lille  in  a  region 
of  distilleries  which  involved  the 
training  of  young  men  to  profici- 
ency in  industrial  chemistry,  and 
made  it  essential  to  get  new  light 
upon  the  various  kinds  of  fermen- 
tation. 
At  this  period  of  Pasteur's  career 

»9 


THE   INFLUENCE  OF  PASTEUR 

the  prevalent  doctrines  of  fermen- 
tation were  singularly  unsatisfac- 
tory anduncontrolled  by  searching 
experimentation.  The  versatile 
Spallanzani  had  nearly  a  century 
before  taken  the  important  step  of 
showing  that  putrescible  liquids 
can  be  permanently  protected  from 
the  processes  of  fermentation  and 
decomposition  by  boiling  and  ex- 
clusion of  air.  Then  Gay-Lussac, 
inspired  by  the  revolutionary  but 
constructive  work  of  Lavoisier, 
made  his  clever  attempt  to  show 
that  the  results  of  Spallanzani  were 
due  to  the  exclusion  of  the  oxy- 
gen of  the  air  from  the  decompo- 
sible  materials,  and  the  ingenious 
French  cook  Appert  put  this  erro- 
neous idea  to  important  practical 
use  in  his  widely  employed  meth- 
od of  canning  perishable  foods. 
Thus  in  the  early  days  of  the  nine- 
teenth century  people  were  con- 

20 


ON   MEDICAL  SCIENCE 

tent  to  think  of  alcoholic  fermen- 
tation as  purely  a  chemical  pro- 
cess. The  first  great  blow  to  this 
widely  accepted  doctrine  came 
from  Theodor  Schwann's  incisive 
studies  of  the  yeast  plant  in  its 
relation  to  alcoholic  fermentation. 
Very  clearly  did  Schwann  show 
that  oxygen  does  not  suffice  to 
initiate  the  fermentation  of  sugar, 
and  that  the  necessary  condition 
is  the  presence  of  something 
which  is  destroyed  by  heat — a  liv- 
ing organism.  Unfortunately,  he 
failed  to  maintain  aggressively  the 
new  doctrine  of  the  dependence 
of  fermentation  on  micro-organic 
life.  The  result  was  that  the  new 
vitalistic  hypothesis  failed  to  make 
any  important  advance  in  the  face 
of  the  sharp  criticism  and  ridicule 
of  so  active  and  influential  a 
teacher  as  Justus  Liebig,  whose 
word  was  nearly  everywhere  re- 

21 


THE   INFLUENCE   OF   PASTEUR 

ceived  as  final  in  matters  chemi- 
cal and  physiological. 

To  Liebig  and  to  many  others 
it  seemed  a  retrograde  step  to  as- 
sume that  a  living  organism  like 
the  yeast  plant  is  the  cause  of  al- 
coholic fermentation,  for  the  most 
advanced  scientific  thinkers  were 
eagerly  striving  to  explain  the 
phenomena  of  life  by  physical  and 
chemical  laws,  and  the  role  of 
''  vital  force  "  was  being  success- 
fully restricted  almost  from  day  to 
day.  Liebig  pointed  effectively  to 
the  fact  that  sugar  undergoes 
other  kinds  of  fermentation  than 
alcoholic,  such  as  lactic  and  buty- 
ric, but  that  nothing  like  a  yeast 
organism  was  to  be  seen  in  these 
allied  types  of  decomposition.  It 
seemed  to  him  that  these  various 
kinds  of  decomposition  had  one 
feature  in  common — the  presence 
of  a  small  quantity  of  nitrogenous 

22 


ON   MEDICAL   SCIENCE 

substance.  This  dead  material 
operated  as  the  real  ferment,  by 
communicating  a  kind  of  shock  to 
the  molecules  of  sugar  or  beef  ex- 
tract with  which  it  came  in  con- 
tact, which  resulted  in  the  frag- 
mentation of  the  molecule  into 
smaller  molecules,  the  essence  of 
fermentation  and  putrefaction. 

To  Pasteur  the  position  of  Lie- 
big  was  wholly  unintelligible  be- 
cause it  rested  on  prejudice  much 
more  than  on  experimental  evi- 
dence. He  resolved  to  investi- 
gate the  subject  of  fermentations 
from  the  standpoint  which  he  had 
reached  by  observing  the  fermen- 
tation of  the  paratartrates — that  is 
to  say,  with  the  preconceived  idea 
that  fermentation  depends  on  the 
mediation  of  living  organisms. 
The  first  notable  paper  in  the  long 
series  which  solved  one  of  the  most 
pressing   questions    in    biology 

23 


THE  INFLUENCE   OF   PASTEUR 

deals  with  lactic  acid  fermenta- 
tion. *  It  might,  perhaps,  have 
been  anticipated  that  Pasteur's 
first  important  utterance  on  the 
nature  of  fermentation  would  deal 
with  the  alcoholic  form  which  has 
so  great  a  commercial  importance. 
He  discovered,  however,  in  lactic 


*  During  the  years  1858  and  1859  Pasteur  did 
highly  important  work  on  alcoholic  fermentation. 
His  views  as  to  the  significance  of  molecular  dissym- 
metry had  already  led  him  to  regard  the  levo-rotary 
action  of  amyl  alcohol  as  an  indication  that  this  reg- 
ular product  of  alcoholic  fermentation  is  formed  by  the 
mediation  of  living  organisms.  It  was,  in  fact,  his 
study  of  amyl  alcohol  (1855)  together  with  the  ex- 
periment on  inactive  ammonium  paratartrate  that  in- 
cited Pasteur  to  undertake  researches  on  the  method 
of  fermentative  processes.  His  superior  chemical  train- 
ing under  Dumas  was  used  to  great  advantage  in  all 
the  researches  on  fermentation.  In  the  case  of  alco- 
holic fermentation  Pasteur  showed  that  the  acid 
formed  is  neither  acetic  nor  lactic  acid,  but  that  suc- 
cenic  acid  and  glycerine  are  regular  and  not  unim- 
portant products.  Lavoisier  and  Gay-Lussac  repre- 
sented the  sugar  in  alcoholic  fermentations  as  splitting 
wholly  into  alcohol  and  carbon  dioxide,  but  the  work 
of  Pasteur  showed  that  five  or  six  per  cent,  of  all  the 
sugar  is  not  decomposed  in  this  way. 

24 


ON   MEDICAL  SCIENCE 

fermentation  an  admirable  field 
on  which  to  contest  the  ideas  of 
Liebig  and  his  followers,  who 
were  constantly  pointing  out  that 
in  lactic  fermentation,  so  like  the 
alcoholic  form,  there  is  nothing 
at  all  like  a  yeast  ferment.  This 
research  ended,  as  is  well  known, 
in  the  discovery  of  a  specific  lac- 
tic acid  organism  or  ferment,  and 
in  the  cultivation  of  this  and  other 
organisms  in  an  artificial  medium 
free  from  albuminoids.  Pasteur 
was  not  slow  in  forming  the  hy- 
pothesis that  different  types  of 
fermentation  are  dependent  on  dif- 
ferent types  of  micro-organisms, 
and  this  idea  of  specificity,  soon 
established  in  relation  to  the  or- 
dinary decompositions,  ultimately 
became  the  basis  of  our  modern 
knowledge  of  the  infectious  dis- 
eases. 
The  research  of  lactic  acid  fer- 


THE   INFLUENCE   OF   PASTEUR 

mentation  thus  gave  the  coup  de 
grace  to  the  chemical  theory  of 
fermentation  at  the  sametime  that 
it  marked  the  birth  of  the  promi- 
sing science  of  bacteriology.  The 
development  of  a  method  de- 
signed to  secure  pure  cultures 
from  fluid  media,  the  use  of  cul- 
ture media  of  known  composi- 
tion, and  the  careful  chemical 
study  of  products  of  decomposi- 
tion all  belong  to  this  early  period 
of  Pasteur's  life,  and  were  achieve- 
ments of  the  deepest  significance 
for  the  future  of  the  great  depart- 
ment of  knowledge  which  has  re- 
vivified the  biological  sciences. 

Another  research  on  fermenta- 
tion deserves  more  than  passing 
notice  on  account  of  the  extraor- 
dinary discovery  which  appears 
as  its  almost  accidental  by-pro- 
duct. This  is  the  investigation  on 
butyric  acid  ferments  (1861).  This 

26 


ON   MEDICAL   SCIENCE 

research  brought  to  light  the  fact 
that  there  are  motile  organisms  ca- 
pable of  inducing  a  decomposition 
of  sugar  with  the  production  of 
butyric  acid.   In  the  course  of  this 
research  Pasteur  saw  that  these 
organisms  (whose  motility  was 
most  puzzling  on  account  of  its 
suggesting  animal  life)  behaved 
very  differently  according  to  their 
position  with  reference  to  thecover 
glass,  those  at  the  centre  being  ac- 
tive, while  those  at  the  periphery 
and   exposed   to  the  air   were 
checked    in  their  movements.* 
From  this  casual  observation  came 
the  fundamental    conception  of 
anaerobic  life.    All  physiologists 
recognize  to-day  ''  a  class  of  be- 
ings possessing  such  vigorous  re- 
spiratory power, "as  Pasteur  aptly 

*  Pasteur  fell  into  the  error  of  describing  the  buty- 
ric acid  organisms  as  infusorians,  and  thought  he  had 
shown  that  animal  life  can  exist  without  oxygen. 

27 


THE   INFLUENCE  OF   PASTEUR 

says,  ' '  that  they  are  able  to  live 
without  the  influence  of  the  air  by 
taking  oxygen  from  certain  com- 
pounds, thus  occasioning  in  the 
latter  a  slow  and  progressive  de- 
composition." 

That  Pasteur's  original  and 
searchingexamination  of  the  prob- 
lem of  fermentation  would  one 
day  lead  him  into  a  controversy 
over  the  unsettled  question  of 
spontaneous  generation  might  al- 
most have  been  predicted.  The 
long  discussion  with  Pouchet  and 
Bastian,  containing  something  of 
bitterness  and  not  a  little  of  the 
ridiculous,  is  a  dramatic  and  ani- 
mated chapter  in  the  life  of  a  peace- 
able but  truth-loving  man.  As 
students  of  the  influence  of  Pas- 
teur on  medical  science  we  need 
not  pause  to  review  this  controv- 
ersy, for  its  fruits  are  to  be  found 
in  all  his  subsequent  work  on  the 
28 


ON    MEDICAL   SCIENCE 

specific  nature  of  the  infectious 
diseases.  Yet  this  discussion,  pro- 
longed over  nearly  twenty  years, 
and  replete  with  instruction  and 
entertainment,  is  worthy  of  a  per- 
manent place  in  the  memories  of 
scientific  men. 

After  a  public  victory  over  Pou- 
chet  in  1862,  which  brought  in  its 
train  the  honor  of  election  to  the 
Academy  of  Sciences,  Pasteur 
turned  his  attention  toward  two 
subjects  of  much  practical  interest 
which  seemed  closely  connected 
with  the  phenomena  of  fermenta- 
tion. One  of  these  was  the  man- 
ufacture of  vinegar,  the  other  the 
diseases  of  wine.  The  study  of 
vinegar  led  to  the  recognition  of 
the  micro-organic  nature  of  the 
vinegar  film  or  mycoderma,  and 
brought  acetic  fermentation  into 
line  with  lactic  and  butyric  fer- 
mentations. It  led  also  to  the  dis- 
29 


THE  INFLUENCE   OF   PASTEUR 

covery  that  the  oxidation  of  alco- 
hol through  the  agency  of  the  vin- 
egar organisms  may  be  carried  too 
far,  acetic  acid  being  lost  by  oxi- 
dation to  water  and  carbon  diox- 
ide. Then  again,  Pasteur  was  able 
to  aid  the  makers  of  vinegar  by 
teaching  them  that  the  indispen- 
sable film  formation  can  be  facili- 
tated by  the  actual  transfer  of  the 
living  ferments  to  the  surface  of 
the  vinegar.  In  the  study  of  the 
diseases  of  wine  Pasteur  achieved 
even  more  helpful  practical  re- 
sults, for  after  recognizing  the  de- 
pendence of  sour,  bitter  and  mud- 
dy wines  on  the  presence  of  defi- 
nite types  of  living  ferments,  he 
was  able  to  suggest  a  simple  and 
efficient  way  of  controlling  these 
disturbing  agencies  by  the  use  of 
moderate  heat.  From  this  recom- 
mendation has  sprung  the  use  of 
the  widely  employed  method  of 

30 


ON    MEDICAL   SCIENCE 

sterilizing  which  we  call  Pasteuri- 
zation. 

In  Pasteur's  growing  interest  in 
these  works  of  practical  utility  we 
can  detect  a  tendency  which  was 
destined  to  bear  rich  fruitage  in 
medical  science — the  inclination 
to  employ  the  gifts  of  which  he 
could  no  longerfail  to  be  conscious 
in  a  manner  likely  to  be  directly 
helpful  in  relieving  the  needs  of 
his  fellow  men.  It  was  this  atti- 
tude which  made  it  possible  in 
1865  to  lead  Pasteur,  not  without 
regret,  away  from  his  studies  of 
fermentation  to  a  wholly  new 
sphere  of  endeavor.  In  that  year 
the  mortality  among  the  silk- 
worms of  northern  France  was  so 
great  that  the  silkworm  industry 
was  threatened  with  total  extinc- 
tion, and  grievous  famine  was 
making  its  appearance  in  a  land 
where  comfort  and  contentment 

3» 


THE   INFLUENCE   OF   PASTEUR 

had  long  reigned.  Dumas,  acting 
for  a  Senate  Committee,  selected 
Pasteur  to  solve  the  mystery  of 
the  plague.  To  Pasteur's  remon- 
strance that  he  knew  nothing  of 
the  subject  and  had  never  seen  a 
silkv/orm  Dumas ansv^ered:  ''So 
much  the  better.  You  v^ill  not 
have  any  ideas  except  those  that 
come  to  you  through  your  own 
observations. "  There  were  many 
unfriendly  comments  on  this  ap- 
pointment, forsome  scientific  men 
could  not  understand  why  achem- 
ist  should  be  chosen  to  cope  with 
an  obscure  zoological  problem. 
But  Dumas  knew  his  man  and 
confidently  relied  on  the  great 
gifts  he  saw  in  him.  It  was  quickly 
evident  that  his  faith  was  not  mis- 
placed. Only  twenty  days  after 
his  arrival  at  Alais,  Pasteur  pre- 
pared a  note  in  which  he  outlined 
a  method  of  breeding  from  the 

32 


ON    MEDICAL  SCIENCE 

eggs  of  silkworms  free  from  dis- 
ease. Unlike  his  predecessors  he 
made  the  moth  the  center  of  the 
efforts  to  regenerate  the  race  of 
silkworms.  'Mf  the  butterfly  is 
sick,  reject  all  its  eggs.*'  It  re- 
quired five  years  of  Pasteur's  most 
devoted  attention,  five  years  be- 
set with  uncertainties  and  disap- 
pointments, to  establish  this  al- 
most clairvoyant  conception  on  an 
incontestable  scientific  basis.  At 
the  end  of  this  period  Pasteur  and 
his  highly  skilled  assistants  had 
shown  that  there  were  two  dis- 
tinct diseases  from  which  the  silk- 
worms died,  pebrine  or  corpuscle 
disease,  and  flacherie,  a  bacterial 
affection  of  intestinal  origin.  The 
former  was  proved  to  be  a  specific 
disease  due  to  the  psorosperm 
Nosema  bombycis  ;  the  latter  was 
believed  by  Pasteur  to  depend  on 
a  specific  bacterium,  but  can  prob- 

33 


THE  INFLUENCE  OF   PASTEUR 

ably  be  excited  by  several  distinct 
varieties  of  bacteria.  The  pebrine 
disease,  which  was  the  chief 
scourge  of  the  industry,  was  erad- 
icated through  the  use  of  a  care- 
ful system  of  breeding  from  eggs 
shown  by  microscopical  exami- 
nation, to  be  free  from  infection. 
The  immense  practical  importance 
of  this  method  sociologically  as 
well  as  financially  can  be  better 
left  to  the  fancy  than  expressed  in 
dollars  and  cents.  But  these  im- 
mediate practical  results  do  not 
adequately  express  the  far-reach- 
ing effects  of  the  great  silkworm 
research,  which  marks  the  entry 
of  Pasteur  into  the  realm  of  animal 
pathology,  and  is  thus  the  vesti- 
bule of  modern  medicine.  For  it 
is  true  that  the  laws  governing  the 
propagation  and  development  of 
the  flacherie  disease  have  the  most 
striking  analogies  to  those  of  the 

34 


ON    MEDICAL   SCIENCE 

diseases  of  man.  The  varying  sus- 
ceptibilities of  different  individ- 
uals to  the  same  micro-organisms, 
the  influence  of  the  path  of  infec- 
tion and  the  fact  that  flacherie  or- 
ganisms acquire  increased  viru- 
lence after  passage  through  the 
bodies  of  living  silkworms  fore- 
shadow discoveries  in  human  pa- 
thology. The  two  volumes  deal- 
ing with  the  diseases  of  silkworms, 
and  dated  1870,  are  works  whose 
contents  should  be  familiar  to 
every  independent  student  of  the 
infectious  diseases. 

The  researches  on  the  silkworm 
diseases  had  one  practical  effect  of 
considerable  importance  for  Pas- 
teur's later  career.  The  success 
with  which  Pasteur  had  solved  his 
intricate  and  widely  known  prob- 
lem made  it  natural  that  French 
investigators  of  animal  pathology 
should  in  future  turn  to  him  as  the 

35 


THE   INFLUENCE   OF   PASTEUR 

man  most  likely  to  help  them  in 
their  work,  and  this  brought  to 
him  new  opportunities  for  fresh 
successes. 

It  is  likely  that  excessive  work 
and  mental  stress  in  some  degree 
contributed  to  the  onset  of  the  se- 
ries of  paralytic  seizures  which  in 
October,  1868,  threatened  the  life 
of  Louis  Pasteur.  During  the  crit- 
ical period  of  his  illness  many  of 
the  most  distinguished  scientific 
men  of  France  vied  with  each 
other  to  share  with  Mme.  Pasteur 
the  privilege  of  nursing  the  man 
they  loved  so  well,  and  of  rescuing 
the  life  that  had  already  placed 
science  and  a  nation  under  endur- 
ing obligation,  through  discover- 
ies which  were  either  of  the  great- 
est practical  utility,  or  appeared 
susceptible  of  almost  unlimited 
development.  Had  Pasteur  died 
in  1868  he  would  have  left  a  name 
36 


ON    MEDICAL   SCIENCE 

immortal  in  the  annals  of  science. 
Others  would  in  some  degree 
have  developed  his  ideas.  Al- 
ready inspired  by  the  researches 
on  fermentation  Lister  would  have 
continued  to  develop  those  life- 
saving  surgical  methods  which 
will  forever  be  associated  with  his 
name.  But  we  may  well  question 
whether  investigations  in  biology 
and  medicine  would  not  have 
been,  for  a  time  at  least,  conducted 
along  less  fruitful  paths.  Who 
shall  say  how  soon  the  great  prin- 
ciple of  experimental  immunity  to 
pathogenic  bacteria,  the  central 
jewel  in  the  diadem  of  Pasteur's 
achievements,  would  have  been 
brought  to  light  ? 

When  Pasteur  recovered  suffi- 
ciently to  resume  work  it  was 
soon  clear  to  apprehensive  frieads 
that  he  had  no  intention  of  leav- 
ing his  ideas  to  be  worked  out  by 

37 


THE   INFLUENCE   OF   PASTEUR 

other  men.  The  miseries  of  the 
Franco-Prussian  war  deeply  af- 
fected him,  and  could  not  fail  to 
inhibit  his  productiveness,  but 
after  a  time  the  unquenchable  love 
for  experimental  research  was 
once  more  ascendant,  and  there 
began  a  new  epoch,  the  epoch  of 
great  discoveries  relating  to  the 
origin  and  cure  or  prevention  of 
the  infectious  diseases  of  man  and 
the  domestic  animals.  As  in  the 
case  of  Ignatius  Loyola^  it  seems 
as  if  the  lamp  of  genius  shone  with 
a  larger  and  more  luminous  flame 
after  the  onset  of  bodily  infirmity, 
in  defiance  of  the  physical  mech- 
anism which  is  too  often  per- 
mitted to  master  the  will. 

The  hostility  of  Pasteur  to  Ger- 
many and  all  things  Teutonic  was 
greatly  intensified  by  the  events 
of  the  Franco-Prussian  war,  and 
has  left  a  somewhat  regrettable 
38 


ON  MEDICAL  SCIENCE 

impression  on  his  scientific  work. 
Desiring  to  contribute  to  the  re- 
habilitation of  his  unhappy  coun- 
try, he  was  led  to  improve  the 
processes  of  brewing,  with  a  view 
to  increasing  the  wealth  of  France, 
and  at  the  same  time  lessening  the 
yearly  tribute  to   the    despised 
people  beyond  the  Rhine.  It  was 
easily  shown  that  some  of  the  dis- 
eases of  beer  are  due  to  the  action 
of  bacteria  allowed  to  take  part  in 
the  process  of  fermentation.    But 
it  soon  became  clear  that  the  mere 
exclusion   of  these  micro-orga- 
nisms does  not  insure  a  brew  of 
good  beer.  The  problem  was  con- 
siderably complicated  by  the  dif- 
ficulty of  deciding  what  consti- 
tutes excellence  in  beer,  and  this 
situation  was  not  helped  by  the 
fact  that  Pasteur,  who  disliked 
the  German  drink  almost  as  much 
as  he  disliked  Germans,  could  not 

39 


THE   INFLUENCE   OF   PASTEUR 

distinguish  one  brew  from  an- 
other. Nevertheless,  after  many 
discouragements,  he  succeeded  in 
establishingmethods  which  much 
improved  the  character  of  French 
beers,  methods  involving  the 
aeration  of  beer-wort  by  sterilized 
air,  and  the  abandonment  of  open 
coolers.  The  results  were  far  from 
satisfactory  owing  to  the  circum- 
stance that  Pasteur  quite  over- 
looked the  part  played  by  the  un- 
desirable forms  of  yeast— so  called 
wild  yeasts — in  the  production  of 
abnormal  fermentations.  In  fact 
it  is  doubtful  if  he  could  have  sep- 
arated the  different  types  of  yeast 
by  the  methods  at  his  command, 
for  even  in  so  late  a  work  as  the  fa- 
mous ''  Etudes  sur  la  Biere,"  bear- 
ing the  date  1876,  we  are  struck 
with  the  inadequate  character  of 
Pasteur's  devices  for  obtaining 
pure  cultures  of  micro-organisms. 
40 


ON   MEDICAL   SCIENCE 

This  work,  with  its  tender  ded- 
ication to  the  memory  of  Pasteur's 
father,  was  a  highly  important 
contribution  to  bacteriology  in 
spite  of  its  many  botanical  defects. 
It  is  really  a  bacteriological  pot- 
pourri bringing  together  the  writ- 
er's views  on  many  questions, 
rather  than  a  strict  treatise  on  the 
diseases  of  beer.  Besides  chapters 
on  the  causes  of  bad  beer  and 
improved  methods  of  brewing, 
the  volume  treats  of  the  origin  of 
ferments  and  furnishes  conclusive 
experimental  evidence  against 
that  plastic  doctrine  of  the  trans- 
formation of  species  around  which 
the  friends  of  the  spontaneous 
generation  fallacy  were  hopefully 
rallying.  But  by  far  the  most 
striking  and  original  chapter  in 
this  notable  volume  is  that  in 
which  Pasteur  formulated  his 
physiological  theory  of  fermenta- 

4» 


THE   INFLUENCE   OF  PASTEUR 

tion — the  startling  theory  that  the 
essential  characfferistic  of  fermen- 
tation is  life  without  air,  life  with- 
out free  oxygen.  This  theory,  if 
not  entirely  upheld  by  other  biol- 
ogists, has  at  least  proved  a  pow- 
erful stimulus  to  new  studies  of 
this  unexplored  aspect  of  life. 

Pasteur's  life  was  prolonged  a 
quarter  of  a  century  after  the  close 
of  the  war  with  Germany,  and 
during  a  large  part  of  this  long 
period  his  mind  dwelt  almost  un- 
ceasingly on  two  phases  of  the 
great  biological  and  practical 
problems  which  it  was  his  for- 
tune to  develop  so  fruitfully.  One 
of  these  was  the  investigation  of 
the  etiology  of  disease  as  related  to 
the  activity  of  micro-organisms. 
The  other  was  the  experimental 
study  of  the  amazing  phenomena 
of  immunity  to  the  action  of  spe- 
cific viruses  or  virulent  micro- 
42 


ON   MEDICAL   SCIENCE 

organisms.  These  two  affiliated 
phases  of  bacteriological  research 
culminated  in  one  of  the  most  re- 
markable discoveries  of  all  time 
—remarkable  for  its  practical  re- 
sults, but  even  more  striking  as 
an  example  of  the  use  of  the  im- 
agination in  science.  It  is  well 
worth  while  to  consider  the  chief 
events  that  ultimately  led  to  the 
discovery  of  a  method  of  immun- 
ization against  the  virus  of  hydro- 
phobia. 

The  idea  that  some  diseases  are 
due  to  living  micro-organisms 
was  suggested  by  Boyle  two  hun- 
dred years  before  the  days  of  bac- 
teriology. From  time  to  time 
thoughtful  men  took  up  this  idea 
as  worthy  of  discussion,  but  it 
received  no  substantial  confirma- 
tion until  Schoenlein,  with  the  aid 
of  the  microscope,  made  his  ad- 
mirable discovery  of  the  infectious 

43 


THE   INFLUENCE   OF   PASTEUR 

nature  of  ring  worm.  This  was  in 
1839.  Within  a  few  years  Henle, 
the  gifted  anatomist  of  Gottingen, 
proposed  an  ingenious  explana- 
tion of  the  infectious  diseases 
which  assumed  the  agency  of 
micro-organisms,  but  the  theory, 
though  based  on  thoughtful  clin- 
ical considerations,  was  deficient 
in  experimental  data  and  had  little 
practical  influence  on  medicine. 
It  is  scarcely  surprising  that  the 
leading  scientific  minds  of  the 
epoch  should  have  been  hostile 
to  any  mere  hypothesis  of  conta- 
gion by  germs,  for  in  their  strug- 
gle against  the  ancient  conception 
of  a  vital  force  they  regarded  the 
idea  of  a  contagium  vivum  exactly 
as  Liebig  had  regarded  Schwann's 
and  Pasteur's  doctrine  of  fermen- 
tation. Even  the  illuminating-cell 
doctrine  of  Virchow  was  not  es- 
pecially favorable  to  the  idea  that 

44 


ON   MEDICAL   SCIENCE 

living  organisms  from  outside  can 
excite  disease  by  fixing  them- 
selves and  developing  in  the 
body.  Pasteur's  training  and  tem- 
perament and  genius  admirably 
fitted  him  not  merely  to  detect 
the  great  central  truth  of  etiology, 
but  to  force  it,  in  spite  of  stub- 
born opposition,  upon  a  doubting 
v/orld  half  stunned  at  the  bold- 
ness of  the  new  doctrine.  But 
while  he  took  a  large  part  in  com- 
pelling this  revolution  in  the  con- 
ception of  disease,  the  way  was 
prepared  by  others,  and  especially 
by  the  fine  observations  of  the 
biologist,  Casimir  Joseph  Da- 
vaine,  and  the  accurate  and  in- 
genious experimental  methods  of 
Robert  Koch. 

Davaine,  while  assisting  the 
clinician,  Rayer,  in  the  study  of 
the  devastating  anthrax  plague  in 
1850,  observed  little  thread-like 

45 


THE   INFLUENCE  OF   PASTEUR 

bodies  in  the  blood  of  animals 
dead  of  this  disease.  Ten  years 
later  Delafond  observed  these  lit- 
tle threads  to  be  living  organisms 
w^ith  the  power  of  multiplying 
outside  the  body.  Thirteen  years 
after  his  first  observations,  Da- 
vaine,  incited  by  Pasteur's  sug- 
gestive work  on  the  butyric  acid 
ferment,  reopened  his  study  of 
anthrax  and  confidently  pro- 
claimed that  the  organisms  he 
had  found  were  the  cause  and 
the  only  cause  of  anthrax.  But 
it  required  the  superior  technique 
of  Koch,  unquestionably,  to  ob- 
tain the  anthrax  organisms  in 
pure  culture,  to  follow  the  cycle 
of  their  development  in  the  ani- 
mal body,  and  thus  to  place  the 
important  discovery  of  Davaine 
on  an  impregnable  scientific  foun- 
dation. Pasteur,  entering  this 
field  a  little  later,  independently 
46 


ON   MEDICAL  SCIENCE 

worked  out  some  of  the  most 
striking  features  of  the  etiology 
of  anthrax,  and  convinced  the 
best  scientific  minds  of  France  of 
the  relationship  between  the  ba- 
cilli of  Davaine  and  the  perpetu- 
ation of  the  anthrax  plague. 

Very  closely  associated  with 
Pasteur's  work  on  anthrax  is  the 
admirable  research  in  which  the 
master,  aided  by  Joubert  and 
Chamberland,  discovered  the  or- 
ganism known  to  us  as  the  bacil- 
lus of  malignant  oedema,  but  de- 
scribed by  its  detectors  as  the 
vibrio  septique,  in  the  same  year 
(1877)  in  which  the  well-known 
publication  on  anthrax  appeared. 
Of  the  many  excellent  features 
for  which  this  research  is  dis- 
tinguished there  are  two  that  de- 
serve especial  mention.  First, 
the  recognition  of  the  septic  vi- 
brio in  the  blood  of  animals  not 

47 


THE   INFLUENCE  OF  PASTEUR 

newly  dead  of  anthrax  was  an 
extremely  important  service  in 
clearing  up  the  gravest  objections 
to  Davaine's  doctrine  of  the  etiol- 
ogy of  anthrax.  Secondly,  the 
observation  that  the  septic  vibrio 
is  anaerobic  affords  the  earliest 
example  of  a  pathogenic  organism 
which  in  its  vegetative  form  is 
inhibited  by  the  presence  of  oxy- 
gen— a  discovery  which  we  may 
reasonably  attribute  to  the  expe- 
rience gained  sixteen  years  before 
with  the  butyric  ferment. 

In  looking  for  fresh  proofs  of 
the  bacterial  origin  of  disease, 
Pasteur  made  some  visits  to  the 
hospitals  of  Paris,  and  thus  came 
into  closer  relations  with  the  prac- 
titioners of  medicine  and  surgery. 
The  alert  and  intellectually  honest 
minds  bade  him  welcome  and 
gave  him  every  help  to  pursue 
his  studies ;  the  conservatives 
48 


ON  MEDICAL  SCIENCE 

looked  at  him  askance,  confi- 
dently set  up  their  time-worn 
theories  against  his  experimental 
proofs,  and  lost  no  occasion  to 
ridicule  the  germ  theory  of  the 
origin  of  disease.  To-day  it  is 
difficult  for  us  to  picture  the  in- 
credulity and  amazement  of  many 
prosperous  and  self-satisfied  prac- 
titioners on  hearing  Pasteur's  an- 
nouncement that  he  had  found 
the  same  pus-exciting  micro-or- 
ganisms (probably  the  staphylo- 
coccus pyogenes  aureus)  in  the 
pus  from  a  series  of  boils  and  in 
the  pus  from  osteomyelitis,  and 
that  these  conditions,  so  different 
in  clinical  character,  are  identical 
as  regards  etiology.  Very  soon 
a  second  bomb  of  the  same  nature 
fell  into  the  conservative  camp, 
with  the  confident  and  even  fervid 
declaration  that  child-bed  fever  is 
a  septicaemia  commonly  due  to  a 

49 


THE   INFLUENCE   OF  PASTEUR 

COCCUS  in  chains  (streptococcus),* 
which  could  be  detected  in  the 
cavity  of  the  uterus,  in  the  blood 
of  the  uterine  sinuses,  and  in  the 
blood  of  living  patients.  The  far- 
reaching  practical  results  of  this 
investigation^  to  which  Pasteur 
devoted  only  one  short  publica- 
tion, are  so  well  known  to  you 
that  they  call  for  no  comment 
here. 

Not  long  after  the  beginning  of 
the  anthrax  study  the  attention 
of  Pasteur  was  directed  to  a  dis- 
ease which  was  destined  to  play 
a  remarkable  part  in  leading  to 
the  great  goal  toward  which  the 
researches  of  the  master  were 
carrying  him — the  discovery  that 
it  is  possible  experimentally  to 


*  Pasteur's  description  of  the  organism  found  in 
puerperal  septicaemia  is  not  enough  to  make  it  cer- 
tain that  he  was  dealing  with  pure  cultures  of  the 
streptococcus  pyogenes. 

50 


ON   MEDICAL  SCIENCE 

induce  immunityto  disease  caused 
by  virulent  micro-organisms.  Per- 
roncito  of  Turin  and  Toussaint  of 
Toulouse  had  reached  the  con- 
clusion that  an  organism  detected 
by  the  former  is  the  cause  of 
chicken  cholera,  but  neither  had 
the  requisite  bacteriological  train- 
ing actually  to  establish  the  cor- 
rectness of  this  contention.  Pas- 
teur was  consulted  on  the  sub- 
ject, and,  bringing  to  bear  his 
superior  knowledge  and  technical 
skill,  succeeded  in  growing  the 
organism  outside  the  animal  body 
and  in  experimentally  inducing 
chicken  cholera  by  means  of  these 
cultures  grown  in  vitro.  Return- 
ing to  the  laboratory  after  a  short 
absence,  he  found  that  his  cultures 
of  the  bacilli  of  chicken  cholera 
had  failed  to  grow  or  had  grown 
only  feebly.  To  increase  the  ac- 
tivity of  these  micro-organisms, 

51 


THE   INFLUENCE   OF   PASTEUR 

they  were  now  inoculated  into 
normal  fowls — a  procedure  sug- 
gested by  previous  experiments 
with  other  bacteria.  The  results 
were  disappointing,  for  the  inoc- 
ulated animals  showed  no  signs 
of  the  disease.  This  made  it  nec- 
essary to  isolate  and  grow  actively 
pathogenic  bacteria  from  animals 
with  chicken  cholera.  Having 
done  this,  it  occurred  to  Pasteur 
that  it  would  be  of  interest  to 
inoculate  with  fresh  and  virulent 
bacilli  the  animals  already  treated 
with  the  attenuated  strain  of 
chicken  cholera  organisms.  This 
was  done  without  delay,  and  to 
his  surprise  nearly  all  of  these 
prepared  animals  resisted  the  vir- 
ulent germs.  They  had  been 
immunized  by  means  of  the  at- 
tenuated cultures  and  a  new  prin- 
ciple had  come  into  medicine.  By 
experimental  study  and  long  re- 

52 


ON    MEDICAL   SCIENCE 

flection  on  the  work  of  Jenner, 
the  mind  of  Pasteur  had  been 
prepared  to  grasp  the  immense 
practical  significance  of  this  dis- 
covery. It  appeared  probable  that 
what  had  been  accomplished  for 
chicken  cholera  could  be  extended 
to  other  diseases.  One  special 
consideration  made  Pasteur  feel 
hopeful  as  to  the  possibility  of 
immunizing  sheep  and  cattle 
against  anthrax.  He  had  noticed 
that  certain  sheep  long  exposed 
to  anthrax  through  grazing  on  in- 
fected pastures  did  not  die  after 
experimental  inoculation  with  a 
virulent  anthrax  culture,  whereas 
previously  unexposed  animals  of 
the  same  herd  died  promptly  after 
such  inoculation.  Moreover,  he 
knew  from  experience  that  fowls 
can  be  immunized  against  chicken 
cholera  by  feeding  them  the  spe- 
cific germs  of  that  disease,  and 

53 


THE   INFLUENCE   OF  PASTEUR 

this  fact  strongly  suggested  a 
similar  explanation  for  the  anthrax 
immunity  which  he  had  noticed. 
With  this  analogy  in  mind,  Pas- 
teur took  the  first  step  toward  the 
preparation  of  a  vaccine  against 
anthrax.  As  in  the  case  of  chicken 
cholera,  he  strove  to  attenuate 
the  specific  organisms  of  the  dis- 
ease. This  he  tried  to  do  in  the 
way  that  had  succeeded  so  well 
in  the  case  of  chicken  cholera — 
that  is,  by  exposing  anthrax  cul- 
tures to  an  abundance  of  oxygen 
at  the  body  temperatures.  But 
Pasteur  found  that  under  these 
conditions  the  anthrax  organisms 
retain  their  virulence,  owing,  he 
believed,  to  their  capacity  to  pro- 
duce resistant  spores.  To  check 
this  growth  of  the  anthrax  spores 
he  successfully  resorted  to  the 
procedure  of  growing  his  cultures 
at  a  temperature  of  42° — 43°  C. 

54 


ON   MEDICAL   SCIENCE 

in  the  presence  of  oxygen.  By 
varying  the  procedure  somewhat 
he  was  able  to  prepare  a  series  of 
anthrax  vaccines  of  different  de- 
grees of  activity,  the  use  of  a  mild 
vaccine  being  followed  by  that  of 
a  stronger  one  in  the  course  of 
immunization. 

The  announcement  by  Pasteur, 
Chamberland  and  Roux  of  a 
method  of  protecting  animals 
against  the  anthrax  scourge  ex- 
cited great  public  interest,  but 
was  in  many  quarters  received 
with  skepticism  and  derision. 
Pasteur  was  invited  to  make  a 
large-scale  public  test  of  his  claims 
near  Melun,  at  the  farm  of  Pouilly- 
le-Fort.  He  accepted  the  chal- 
lenge gladly,  and  on  May  5,  1881, 
began  a  series  of  public  inocula- 
tions which  will  always  be  mem- 
orable in  the  annals  of  medical 
science.  The  publicity  with  which 
55 


THE  INFLUENCE  OF   PASTEUR 

the  unique  experiment  was  per- 
formed, the  unconcealed  hostility 
and  suspicion  of  many  of  the  on- 
lookers, and  the  alternating  hopes 
and  fears  of  Pasteur,  have  been 
most  entertainingly  described  by 
M.  Vallery-Radot.  The  outcome 
was  a  convincing  demonstration 
of  the  practicability  of  Pasteur's 
method  of  immunizing  against 
anthrax  in  sheep.  Nevertheless, 
two  years  later,  in  an  ill-natured  at- 
tack on  Pasteur's  work,  Koch  at- 
tributed the  discovery  of  vaccina- 
tion against  anthrax  to  Toussaint, 
and  pointed  to  a  paper  in  which 
the  latter  had  reported  some  ex- 
periments describing  the  immuni- 
zation of  dogs  and  sheep  by  means 
of  anthrax  bacilli  which  had  been 
heated  at  55°  C.  for  ten  minutes. 
While  it  is  true  that  Toussaint 
thus  immunized  animals  against 
virulent  anthrax  organisms,  his 

56 


ON   MEDICAL   SCIENCE 

method  of  obtaining  a  vaccine 
was  unreliable  and  unsuited  for 
practical  use.  The  fact  is  that 
Toussaint,  stimulated  by  Pas- 
teur's discovery  of  a  method  for 
immunizing  against  chicken  chol- 
era, prepared  a  vaccine  which 
sometimes  protected  against  the 
disease,  but  which  was  danger- 
ous, owing  to  uncertainty  as  to 
the  number  and  condition  of  the 
living  anthrax  organisms  which 
it  contained.  His  publication  ap- 
peared six  months  after  that  of 
Pasteur,  who,  although  greatly 
interested  in  the  observation  of 
Toussaint,  criticised  the  methods 
of  the  latter  and  ultimately  pre- 
pared a  safe  vaccine  consisting  of 
definitely  attenuated  anthrax  or- 
ganisms. The  crude  experiments 
of  Toussaint  were  wholly  based 
on  the  epoch-making  immuniza- 
tion to  chicken  cholera. 

57 


THE   INFLUENCE  OF   PASTEUR 

On  March  15,  1882,  Louis  Thu- 
illier,  the  earnest  and  gifted  but 
ill-fated  young  assistant  of  Pas- 
teur, discovered  in  the  blood  of 
swine  dead  of  erysipelas  (rouget 
de  pore)  an  organism  which  ap- 
peared to  be  the  active  agent  of 
this  plague — an  organism  which 
Klein  in  his  elaborate  investiga- 
tion had  quite  overlooked,  but 
which  was  independently  discov- 
ered by  Detmers  of  Chicago.  Pas- 
teur had  inspired  this  fine  research 
of  Thuillier  and  stood  ready  to 
develop  it.  By  carrying  the  sus- 
pected organism  through  many 
generations  on  veal  bouillon,  and 
finally  introducing  it  into  hogs, 
the  true  swine  erysipelas  was 
readily  induced.  The  real  prob- 
lem, however,  was  to  make  an 
attenuated  virus  for  the  purpose 
of  immunizing  against  the  dis- 
ease.   Pasteur  succeeded  in  ob- 

58 


ON   MEDICAL   SCIENCE 

taining  a  virus  capable  of  protect- 
ing certain  races  of  hogs  for  a 
period  of  a  year  or  more,  and  this 
important  practical  success  is  ren- 
dered especially  noteworthy  by 
the  method  that  was  followed  in 
attenuating  the  rouget  organisms. 
In  1887  he  had  found  in  the  saliva 
of  rabid  dogs  an  organism  highly 
virulent  for  rabbits  (micrococcus 
of  rabbit  septicaemia).*    Adult 
guinea  pigs  were  immune,  but 
>oung  guinea  pigs  quickly  died 
after  inoculation.    By  passing  the 
organism    through    a   series  of 
young  guinea  pigs  it  gained  in 
virulence  until  it  grew  fatal  for 
adult  guinea  pigs.  But  the  modi- 
fication   which    especially    im- 
pressed Pasteur  was  that  the  bac- 
teria which  had  thus  gained  in 
pathogenic  qualities   for  guinea 


*  Micrococcus  lanceolatus. 
59 


THE   INFLUENCE  OF   PASTEUR 

pigs  had  at  the  same  time  be- 
come attenuated  for  rabbits. 

The  memory  of  this  singular 
observation  now  came  to  his  aid 
in  the  rouget  research.  After  pass- 
ing the  rouget  bacteria  through  a 
series  of  pigeons  (which  are  nat- 
urally susceptible),  it  was  found 
that  the  blood  from  the  last  pig- 
eon had  become  much  more  path- 
ogenic for  swine  than  blood  from 
hogs  dead  of  swine  erysipelas. 
On  the  other  hand,  Pasteur  dis- 
covered that  while  the  passage  of 
the  rouget  organisms  through  a 
series  of  rabbits  (which  are  not 
naturally  susceptible)  permitted 
these  bacteria  to  grow  more  read- 
ily in  the  blood  of  rabbits  and  to 
become  more  highly  pathogenic 
for  them,  they  became  definitely 
and  permanently  diminished  in 
virulence  for  swine.  Thus,  after 
inoculation  with  modified  organ- 

60 


ON   MEDICAL   SCIENCE 

isms,  hogs  became  ill,  but  did  not 
die.  On  their  recovery  they 
were  immune  to  fatal  rouget. 
The  genius  of  Pasteur  thus  gave 
to  biological  science  a  definite 
method  of  permanently  modify- 
ing the  pathogenic  characters  of 
certain  micro-organisms.  This 
contribution  is  recorded  in  a  paper 
w^hich  won  the  applause  of  the 
Academy  of  Medicine,  and  which 
even  to-day  excites  admiration 
for  its  mingling  of  experimental 
skill  and  scientific  imagination. 

So  far  back  as  1880,  in  the  midst 
of  the  exacting  anthrax  investi- 
gation, Pasteur  had  found  time  to 
begin  a  new  research  on  the  pro- 
tective action  of  attenuated  virus. 
From  modest  beginnings  this  re- 
search grew  in  the  hands  of  the 
master  to  be  the  crowning  work 
of  his  life,  in  the  sense  of  em- 
bodying the  fullest  and  in  some 
61 


THE   INFLUENCE   OF  PASTEUR 

respects  most  original  expression 
of  his  ideas  on  the  use  of  experi- 
mentally enfeebled  viruses  for  the 
mitigation  of  infectious  processes. 
The  transmission  of  rabies  thro  ugh 
bites  made  probable  the  infectious 
nature  of  the  disease  and  encour- 
aged a  hope  that  it  would  not  be 
very  difficult  to  isolate  the  specific 
organism  from  the  saliva  of  rabid 
dogs.  But  the  most  systematic 
efforts  to  isolate  such  an  agent 
were  rewarded  only  by  failure. 
To  this  disappointment  was  added 
a  second,  even  more  disconcert- 
ing. It  was  found  that  the  ex- 
perimental transmission  of  the 
disease  by  means  of  saliva  is  a 
matter  of  great  uncertainty.  More- 
over, the  uniformly  fatal  outcome 
of  hydrophobia  made  it  impossi- 
ble to  form  any  opinion  as  to 
whether  the  unknown  virus  was 
capable  of  conferring  immunity. 
62 


ON   MEDICAL   SCIENCE 

Many  an  investigator  would  have 
been  deterred  from  the  prosecu- 
tion of  an  enterprise  so  unprom- 
ising, but  the  interest  of  Pasteur 
had  been  fully  enlisted  before  he 
realized  the  difficulties  of  the 
problem,  and  the  tenacity  of  his 
nature  urged  him  to  keep  pa- 
tiently on  his  course.  He  saw 
clearly  that  a  reliable  way  must 
be  found  to  communicate  rabies 
experimentally,  and  acting  on  a 
suggestion  made  by  Dr.  Dubue 
of  Pau,  that  the  disease  is  essen- 
tially one  of  the  central  nervous 
system,  Pasteur  took  small  bits 
of  nervous  tissue  from  animals 
dead  of  rabies  and  placed  them 
under  the  skin  of  experimental 
animals.  This  method  was  no 
considerable  improvement  on 
similar  inoculations  of  saliva  from 
rabid  dogs,  but  it  served  as  the 
clew  to  a  notable  advance.    This 

6) 


THE   INFLUENCE   OF   PASTEUR 

was  the  introduction  of  rabic 
nerve-tissue  directly  into  the  cen- 
tral nervous  system  of  the  animal 
to  be  infected,  a  procedure  based 
on  the  idea  that  since  rabies  be- 
haves like  a  disease  of  the  nerv- 
ous system  the  micro-organisms 
causing  it  would  be  likely  to  find 
in  the  nervous  system  a  living 
culture  medium  highly  favorable 
to  their  growth.  The  acute  in- 
telligence of  the  masterful  experi- 
mentalist is  strikingly  illustrated 
by  the  fact  that  failure  to  isolate 
specific  micro-organisms  had  not 
shaken  his  faith  in  the  testworth- 
iness  of  his  preconceived  idea. 
Hence,  when  he  found  that  hy- 
drophobia regularly  followed  sub- 
dural inoculation  with  rabic  nerv- 
ous material,  he  was  more  pleased 
than  surprised.  The  first  dog  thus 
inoculated  showed  unmistakable 
signs  of  rabies  after  fourteen  days, 

64 


ON  MEDICAL  SCIENCE 

and  other  animals  gave  similar 
results.  Moreover,  on  bringing 
into  practice  the  experience  he 
had  gained  in  studying  swine  ery- 
sipelas, Pasteur  found  that  he 
could  increase  the  pathogenic 
properties  of  the  virus  by  carry- 
ing it  subdurally  through  a  series 
of  rabbits  or  reduce  it  for  dogs  by 
carrying  it  subdurally  through  a 
series  of  monkeys.  He  thus  had 
at  his  command  three  different 
viruses  —  a  virus  of  natural 
strength,  a  virus  of  increased 
virulence  and  an  attenuated  virus. 
Later  experiments  showed  that  a 
safer  virus  could  be  prepared  by 
drying  over  caustic  potash,  at 
21°  C.,the  spinal  cords  of  rabbits 
dead  of  rabies. 

By  injecting  subcutaneously 
first  a  weak  virus  and  subse- 
quently a  stronger  one  into  parts 
with  very  few  nervous  structures, 

65 


THE   INFLUENCE  OF   PASTEUR 

Pasteur  succeeded  in  immunizing 
dogs  against  otherwise  fatal  sub- 
dural inoculations.  This  success 
suggested  the  possibility  of  im- 
munizing human  beings.  The  rel- 
atively long  duration  of  the  period 
of  incubation,  which  is  commonly 
about  forty  days,  made  the  outlook 
for  human  immunization  peculiar- 
ly promising.  The  opportunity  for 
trying  the  method  soon  appeared 
in  the  person  of  the  little  Alsatian 
lad  Joseph  Meister,  who  came  to 
Paris  with  fourteen  wounds  in- 
flicted by  a  rabid  dog.  Pasteur 
courageously  resolved  to  make  an 
effort  to  rescue  the  bitten  child 
from  the  certain  death  to  which 
he  was  doomed,  by  making  suc- 
cessive injections  of  rabbit  viruses 
of  increasing  strength.  The  result 
is  known  to  all  the  world  ;  the  ef- 
fort to  utilize  the  long  period  of 
incubation  quickly  to  establish  im- 

66 


ON   MEDICAL   SCIENCE 

munity  through  repeated  inocula- 
tions, proved  a  success,  not  only 
in  the  case  of  little  Meister,  but  in 
many  thousand  other  instances. 

The  great  research  on  rabies  fit- 
tingly marks  the  culmination  of 
Pasteur's  long  career  as  an  inves- 
tigator. In  that  investigation  can 
be  seen  the  same  technical  skill, 
the  same  respect  for  minute  detail, 
and  the  same  pertinacity  that  had 
distinguished  so  many  earlier  re- 
searches, but  there  can  be  seen 
also  a  degree  of  originality  and  a 
fertility  of  resource  that  excel 
nearly  all  previous  exhibitions  of 
these  powers.  The  accumulated 
experience  of  a  quarter  century  of 
original  study  of  micro-organic 
life  served  as  liquid  intellectual 
capital  on  which  Pasteur  drew  for 
guidance  at  every  turn  in  the  ex- 
traordinarily intricate  and  perplex- 
ing study  of  rabies.  And  it  seems 
67 


THE  INFLUENCE  OF  PASTEUR 

wholly  clear  that  this  new  discov- 
ery could  never  have  been  made 
without  such  a  treasure  of  experi- 
mental experience. 

One  who  looks  only  at  the  re- 
sults of  Pasteur's  far-reaching 
work  is  apt  to  overlook  his  mis- 
takes and  shortcomings,  and  to 
forget  that  he  made  some  serious 
errors  not  only  in  the  interpreta- 
tion of  experimental  data,  but 
sometimes  also  in  experimental 
technic.  To  pathologists  of  the 
present  day  Pasteur's  conception 
of  acquired  immunity  appears  so 
crude  that  it  is  difficult  to  believe 
he  ever  entertained  it  seriously. 
His  work  on  chicken  cholera  na- 
turally led  him  to  form  a  theory  to 
account  for  the  immunization 
which  he  observed,  and  this  the- 
ory was  that  immunity  arises  from 
the  inability  of  a  pathogenic  or- 
ganism to  grow  in  a  medium  in 

68 


ON   MEDICAL  SCIENCE 

which  it  has  previously  devel- 
oped. Animals  thus  become  im- 
mune because  the  necessary  nu- 
trient material  for  the  multiplica- 
tion of  the  specific  organisms  has 
been  used  up,  just  as  an  organism 
w^ill  after  a  time  cease  to  grow  in 
vitro  in  an  old  culture  medium. 
it  seems  strange  that  he  did  not 
test  this  theory  by  trying  to  grow 
the  organisms  outside  the  body 
in  the  blood  and  serum  of  both  the 
immunized  and  normal  animals, 
and  so  learn  that  he  was  in  error. 
The  short  and  usually  inadequate 
descriptions  of  micro-organisms 
which  Pasteur  has  given  in  his 
terse  publications  have  aroused 
much  criticism  from  bacteriolo- 
gists, and  it  cannot  be  denied  that 
he  underrated  the  importance  of 
minute  morphological  andcultural 
studies — studies  without  which 
some  of  the  most  important  mod- 
69 


THE   INFLUENCE   OF  PASTEUR 

ern  advances  could  not  have  been 
made.  Nor  is  it  easy  to  explain  the 
reluctance  with  which  he  adopted 
the  improved  bacteriological  tech- 
nique of  other  investigators. 
Koch's  method  of  plating  bac- 
teria, Weigert's  and  Ehrlich's 
methods  of  staining  and  certain 
important  nutrient  media  found 
their  way  into  his  laboratory  only 
after  long  delay,  and  through  the 
efforts  of  assistants.  Pasteur's 
comparatively  faulty  technique 
for  obtaining  pure  cultures  of  bac- 
teria is  doubtless  responsible  for 
many  of  the  disheartening  results 
reported  by  foreign  observers  who 
used  his  vaccines.  Nevertheless 
his  methods  in  the  main  served 
their  purpose  well,  and  we  should 
remember  that  the  most  finished 
instruments  cannot  belong  to  the 
pioneer  who  makes  his  own  tools. 
Fortunately  Pasteur  was  greatly 
70 


ON   MEDICAL  SCIENCE 

favored  by  the  circumstance  that 
in  many  of  his  etiological  studies 
he  made  cultures  from  the  blood, 
where  the  specific  micro-organ- 
isms often  existed  in  pure  cul- 
ture. 

Although  even  the  plainest  nar- 
rative of  Pasteur's  individual 
achievements  is  proof  enough  that 
his  work  holds  a  unique  position 
in  the  history  of  biological  sci- 
ence, it  is  worth  while  to  consider 
in  more  general  terms  what  it  was 
that  the  consummate  experiment- 
alist added  to  the  science  of  med- 
icine. Such  a  consideration  gives 
us  a  more  just  measure  of  his  in- 
fluence than  the  most  detailed  re- 
cital of  specific  investigations.  If 
we  would  understand  the  influ- 
ence of  Pasteur  on  medical  science 
we  must  recognize  that  his  exam- 
ple as  the  apostle  of  an  almost  un- 
tried method  of  approaching  the 

71 


THE   INFLUENCE  OF  PASTEUR 

problems  of  medicine  has  been  no 
less  enlightening  than  his  actual 
discoveries.  Emerson  has  said  : 
''  Great  men  exist  that  there  may 
be  greater  men."  The  recent  his- 
tory of  medicine  in  the  United 
States  as  well  as  in  Europe,  plainly 
shows  that  the  seed  of  example 
sown  by  Pasteur  has  already  fal- 
len on  receptive  soil,  from  which 
have  sprung  new  combinations  of 
human  faculties  powerful  for  the 
amelioration  of  human  life.  Our 
country  has  no  greater  cause  for 
satisfaction  than  the  knowledge 
that  the  ideality  as  well  as  the 
methods  of  Pasteur,  has  inspired 
a  growing  circle  of  original  inves- 
tigators in  medical  science  who 
labor  for  the  common  welfare. 
Let  us  hope  that  this  circle  will  be 
continually  widened,  in  the  future 
as  in  the  past,  by  accessions  from 
the  students  of  this  University, 
72 


ON   MEDICAL  SCIENCE 

where  the  best  idealsof  work  have 
been  so  richly  nurtured. 

Perhaps  the  most  deeply  signif- 
icant feature  of  Pasteur's  contri- 
butions to  medicine  is  their  direct 
dependence  on  the  principles  of 
physics  and  chemistry,  the  scien- 
ces that  so  often  lie  at  the  heart 
ofreal  advances  in  biology.  Med- 
ical men  trained  alongthe  conven- 
tional semi-scholastic  lines  had 
often  dabbled  with  these  funda- 
mental sciences,  and  sometimes 
the  superficial  contact  had  yielded 
creditable  or  even  important  re- 
sults. In  many  instances,  also, 
truly  great  advances  had  come 
from  the  labors  of  men  who  like 
Malpighi,  Bichat  and  Johannes 
Miiller  were  wide  awake  to  the 
fact  that  sound  medicine  must  rest 
on  sound  biological  conceptions. 

But  despite  the  activity  of  nu- 
merous gifted   medical  men  of 

73 


THE  INFLUENCE   OF   PASTEUR 

broad  scientific  sympathies,  the 
medical  profession  at  the  begin- 
ning of  Pasteur's  career  was  dully 
followinga  well  trodden  but  nearly 
blind  road,  in  the  hopeless  strug- 
gle to  solve  the  intricate  problems 
of  human  pathology  and  physiol- 
ogy by  minute  observations  and 
experiments  confined  largely  to 
the  most  complex  representatives 
of  animal  life.  Then  for  the  first 
time  there  appeared  in  the  biolog- 
ical sciences  a  man  profoundly 
trained  in  the  methods  of  chem- 
istry and  physics,  and  inspired, 
moreover,  with  a  firm  confidence 
in  the  applicability  of  these  sci- 
ences to  the  solution  of  biological 
and  medical  problems.  Triply 
armed  with  a  sound  method,  a 
lofty  imagination,  and  a  strong 
will  to  serve  his  country,  Louis 
Pasteur  entered  the  wide  arena  of 
medical  research,  to  win  there  the 

74 


ON    MEDICAL   SCIENCE 

triumphs  that  have  reconstituted 
medicine,  and  have  secured  him 
an  undying  fame.     Step  by  step, 
with  rigid  logic  and  unfaltering 
determination,  he  passed  from  the 
early  crystallographic  discoveries 
to  the  new  conception  of  fermen- 
tation, and  from  this  to  the  crucial 
discoveries  relative   to  etiology 
and  immunity  for  which  the  med- 
ical sciences  had  waited  so  long. 
To  have  fought  the  long  battle 
of  life  with  unwavering  constancy 
to  the  loftiest  ideals  of  conduct, 
toiling    incessantly    without    a 
thought  of  selfish  gain  ;  to  have 
remained  unspoiled  by  success 
and  unembittered  by  opposition 
and  adversity  ;  to  have  won  from 
nature  some  of  her  most  precious 
and  covert  secrets,  turning  them 
to  use  for  the  mitigation  of  human 
suffering  :— these  are  proofs  of 
rare  qualities  of  heart  and  mind. 

75 


THE  INFLUENCE   OF   PASTEUR 

Such  full  success  in  life  did  Louis 
Pasteur  attain,  and  from  the  con- 
sciousness of  good  achieved,  his 
noble  nature  found  full  reward  for 
all  his  labor. 

Of  the  children  whom  fortune 
has  endowed  with  splendid  gifts, 
there  are  few  whose  lives  have 
affected  so  profoundly  and  so  be- 
neficently the  fate  of  their  fel- 
lows, few  who  have  earned  in 
equal  degree  the  gratitude  and 
reverence  of  all  civilized  men.  Al- 
though not  many  can  hope  to  en- 
rich science  with  new  principles, 
all  of  us  may  gain  from  Pasteur's 
life  the  inspiration  to  cultivate  the 
best  that  is  in  us.  Let  us  keep 
living  in  our  memories  the  inspir- 
iting words  which  the  master 
spoke  on  the  seventieth  anniver- 
sary of  his  birthday:  ''Young 
men,  young  men,  devote  your- 
selves to  those  sure  and  powerful 

76 


ON   MEDICAL   SCIENCE 

methods,  of  which  we  as  yet  know 
only  the  first  secrets.  And  I  say 
to  all  of  you  whatever  may  be 
your  career,  never  permit  your- 
selves to  be  overcome  by  degrad- 
ing and  unfruitful  scepticism. 
Neither  permit  the  hours  of  sad- 
ness which  come  upon  a  nation  to 
discourage  you.  Live  in  the  se- 
rene peace  of  your  laboratories  and 
your  libraries.  First  ask  your- 
selves, what  have  I  done  for  my 
education  ?  Then  as  you  advance 
in  life,  what  have  I  done  for  my 
country  ?  So  that  some  day  that 
supreme  happiness  may  come  to 
you,  the  consciousness  of  having 
contributed  in  some  manner  to 
the  progress  and  welfare  of  hu- 
manity. But,  whether  our  efforts 
in  life  meet  with  success  or  failure, 
let  us  be  able  to  say  when  we  near 
the  great  goal,  '  I  have  done  what 
I  could.' " 

77 


E  DATE 


1992  NCV2  5199l> 


Printed 
in  USA 


COLUMBIA  UNIVERSITY  LIBRARIES 


0037525271 


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